Safety device for liquid fuel burner



April 7, 1970 J. M. DUNSTON SAFETY DEVICE FOR LIQUID FUEL BURNER 2Sheets-Sheet 1 Filed Aug. 23, 1968 Q m 2 ii I h l/ll/f ///////////I/////W\ mm mm.

0 0 0 0 n.r\ x SiFE-- c @x April 7, 1970 J. M. DUNSTON SAFETY DEVICE FORLIQUID FUEL BURNER 2 Sheets-Sheet 2 Filed Aug. 23, 1968 United StatesPatent 3,504,687 SAFETY DEVICE FOR LIQUID FUEL BURNER James M. Dunston,Natick, Mass., assignor to the United States of America as representedby the Secretary of the Army Filed Aug. 23, 1968, Ser. No. 754,885 Int.Cl. F16k 17/14; F23n ]/00 US. Cl. 13768 Claims ABSTRACT OF THEDISCLOSURE A safety device for a liquid fuel burner having a reservoircapable of being filled with liquid fuel under pressure up to apredetermined level providing a vapor space above the liquid fuel in thereservoir comprising a fuel feed tube for conducting liquid fuel fromthe reservoir to the burner, the fuel feed tube being mechanicallyrupturable at a predetermined point within the vapor space upondeformation of the reservoir wall caused by pressure within thereservoir to cut off the flow of liquid fuel from the reservoir to theburner.

The invention described herein, if patented, may be manufactured andused by or for the Government for governmental purposes, without thepayment to me of any royalty thereon.

This invention relates to a safety device for liquid fuel burners,particularly gasoline burners, to prevent excessive pressure buildup inthe fuel tanks thereof and to minimize the possibility of explosion.

In outdoor camping activities and military field operations, pressurizedliquid fuel burners are often used for heating and cooking purposes.Such burners range in size from very compact stoves having a capacity ofabout 2,500 B.t.u. per hour for use by individuals or small groups torelatively large and complex burner units used by the military incooking and baking for large groups, such as the Burner Unit, GasolineField Range Outfit described in Military Specification MlLB 40098C datedJuly 12, 1967, which has a capacity of about 55,000 B.t.u. per hour. Allof these burners have certain common characteristics including a closedfuel tank or reservoir, means for creating a pressure greater thanatmospheric with the tank and a fuel filling device which preventscomplete filling of the tank. The latter device insures a minimum vaporspace above the level of the liquid fuel in the tank at all times. Thisvapor space provides for safe expansion of the fuel under normaloperating conditions as the temperature of the fuel rises due to theproximity of the burner where combustion is occurring.

When the unit is operating, fuel is drawn from the lower portion of thetank through a fuel feed tube to a generator or vaporizer wherein theliquid fuel is converted to vapor prior to being fed to the burner inorder to provide for more efficient combustion. Because of therequirement for portability of such equipment, the fuel tanks, thegenerator and the burner are usually arranged in close proximity to oneanother to provide a compact unit. In this arrangement, considerableheat is reflected or radiated from the burner and the container beingheated above the burner and heat is conducted from the generator andother parts of the unit to the fuel tanks. The resulting increase in thetemperature of the liquid fuel and fuel vapors in the tank causes anincrease in the pressure within the tank. When a burner unit is used ator near its heating capacity for heating a large container and to aneven greater extent when the unit is used within a field range cabinetor field oven, the danger of excessive pressure buildup in the tankswith the possibility of explosion is a recognized problem. Closesurveillance of the burner may permit corrective ice action by reducingthe rate of combustion in the burner. However, such surveillance is notalways possible in actual operation since distraction or, in the case ofmilitary operations, operating conditions may not permit closeattention.

It is therefore an object of the present invention to provide a meansfor the prevention of explosions of fuel tanks in gasoline fired fieldrange burner units.

Another object of the invention is to provide a safety device which willautomatically cut off the supply of liquid fuel from a fuel tank to aburner unit in a gasoline field range when the pressure in the fuel tankreaches a predetermined level.

A further object of the invention is to provide a safety device whichwill automatically reduce the pressure within the fuel tank of apressurized gasoline burner by discharging combustible vapors fromwithin the tank through the burner for normal combustion.

A still further object of this invention is to provide a safety devicefor pressurized gasoline burners which is tamper-proof in that it cannotbe by-passed or rendered inoperative.

A still further object of this invention is to provide a safety devicewhich may be simply and inexpensively replaced after it functions.

Various other objects and advantages derived from the invention will beapparent from the following description of one embodiment of theinvention and from the appended claims.

The foregoing objects are accomplished by providing a fuel feed tubewhich is mechanically rupturable at a predetermined point thereon abovethe level of liquid fuel in the tank and means mounted within thefuel'tank for rupturing the fuel feed tube upon the occurrence of apredetermined pressure within the fuel tank. The supply of liquid fuelto the generator is cut off when the fuel feed tube is ruptured and thefuel rich vapors in the upper part of the fuel tank are passed throughthe generator to the burner where they are safely consumed.

The present invention may be more fully understood by reference to theaccompanying drawing showing one embodiment of the invention, whereinlike reference characters designate like parts in the various views, andin which:

FIGURE 1 is a vertical plan view, partially in section, of a gasolineburner unit of the type covered by the abovementioned MilitarySpecification MIL-B-40098C, modified in accordance with the presentinvention.

FIGURE 2 is a partial horizontal section of the fuel tank and fuel feedtube of the gasoline burner unit shown in FIGURE 1, with portions of thefuel tank broken away, along the plane 22 of FIGURE 1; and

FIGURE 3 is an enlarged vertical sectional view, with portions brokenaway, of the fuel feed tube, the indented portion of the sidewall of thefuel tank, and the fuel feed tube connecting member, as seen in FIGURE 1with the position of these elements after operation of the safety devicebeing shown in broken lines.

Referring more particularly to FIGURE 1, the burner unit comprises agenerally tubular frame 4, a fuel tank 5 supported by clamps (not shown)attached to the tubular frame, a generator assembly 6, a fuel feed tube7, a burner head 8, a mixing chamber assembly 9, a needletype controlvalve 10, an air valve 11, a pressure indicating gage 12, and a topshield assembly 13. In addition, such units are generally provided withpreheater means and an air pump, which have been omitted from thedrawings for purposes of clarity. The generator assembly 6 extends overthe burner head 8 such that the heat from the flame at the burner headserves to vaporize the liquid fuel passing through the generatorassembly prior to its being introduced into the mixing chamber 14 andthence to the burner head.

The fuel tank 5 is preferably generally U-shaped and has a generallycylindrically shaped cross-section except through a portion of the bightof the U-shaped tank. One arm of the U-shaped fuel tank has a fillingdevice comprising a filler tube (not shown) extending therethrough tothe interior of the fuel tank. The configuration of the filler tubeprovides a means for introducing liquid fuel into the fuel tank up to apredetermined maximum level which assures a minimum air space in thetank above the level of the fuel. The filler tube is closed by a fillercap assembly (not shown). As shown in FIGURES 1, 2 and 3, an indentedportion is formed in the sidewall of the fuel tank at the bight of theU. This indented portion is conformed to expand or deform outwardly whenthe pressure within the fuel tank increases to a level which issubstantially above normal operating levels but safely below pressurelevels which would cause the tank to rupture. For example, in the burnerunit described in Military Specification MILB-40098C, which has a normaloperating pressure of 30 p.s.i.g., outward movement of the indentedportion of the tank occurs between 90-125 p.s.i.g. while rupture of thetank would occur at about 350 p.s.i.g.

The generator assembly 6 is composed of an elongated tubular member 16which is preferably filled with chopped steel wool fiber which serves asboth a heat transfer and filtering medium, whereby the liquid fuelpassing through the generator assembly is vaporized and some fueladditives, particularly tetraethyl lead, are filtered out.

The front end of the elongated tubular member 16 is provided with adownwardly extending tube 17 which connects the generator assembly tothe control valve 10. The rear end of the elongated tubular member 16 isprovided with a downwardly extending tube 18 including a flanged lowerend portion 19 which cooperates with nut 20 to attach the generatorassembly to the fuel feed tube 7 and the fuel tank 5 at bushing 21.

The fuel feed tube 7 is comprised of a flanged upper end portion 22 andan elongated cylindrical tube 23 joined to flanged upper end portion 22and extending downwardly to a point near the bottom of the fuel tank.The fuel feed tube cooperates with bushing 21, flanged lower end portion19, and nut 20 to connect the fuel feed tube with downwardly extendingtube 18. The elongated cylindrical tube 23 is preferably cut or formedat an oblique angle at its lower end and has a weakened portion 24,preferably formed by a V-shaped cut, which extends substantiallycompletely around the circumference of tube 23 at a level which is abovethe normal maximum level of the liquid fuel in the fuel tank and,therefore, within the vapor space 25 above the liquid fuel. The weakenedportion 24 in the form of a V-Shaped cut has a depth such that, if thetube 23 is bent appreciably, it will rupture at the weakened portion 24.A cut having a depth of approximately half the thickness of the sidewallof tube 23 has been found suitable for this purpose.

As shown in FIGURES 1, 2, and 3 a connecting member 26 in the form of aflat piece of metal bent to form an angle is welded or otherwiseattached to the sidewall of the fuel tank at the interior surface ofindented portion 15. Arm 27 of the connecting member extends inwardly ofthe fuel tank and has a bore 28 through which tube 23 passes in a snuglyfitting relation. Connecting member 26 is attached to indented portion15 at such a level that arm 27 will be appreciably below weakenedportion 24 of tube 23. As a result of this arrangement, when theindented portion of the fuel tank expands outwardly due to excessivepressure within the fuel tank, as discussed above, the connecting member26 pulls and bends tube 23 until the latter ruptures at weakened portion24, as discussed above. This automatically stops the flow of liquid fuelfrom the fuel tank through the fuel feed tube into the generatorassembly, only the fuel vapors in the vapor space 25 above the liquidfuel being able to flow through the ruptured fuel feed tube into thegenerator assembly and thence to the burner head. This has the immediateeffect of reducing the pressure within the fuel tank to a safe level andvery soon thereafter the flame is extinguished because of lack ofsufficient fuel vapors passing through the burner to maintain operationthereof.

In the operation of the burner unit described, the fuel tank 5 is filledwith gasoline to the level permitted by the filling device, leavingvapor space 25 in the fuel tank. The filling device and the controlvalve 10 are then closed. The fuel tank is pressurized by means of anair pump (not shown) connected to air valve 11 to a pressure of about 25p.s.i.g. The front portion of the generator assembly is heated by thepreheating means (not shown). When sufficient preheating has takenplace, control valve 10 is opened, permitting liquid fuel to flow fromfuel tank 5 upwardly through fuel feed tube 7 into generator assembly 6where it is vaporized, the fuel vapors passing through control valve 10into mixing chamber 14 where air is mixed with the fuel vapors. Themixture of fuel vapors and air then passes upwardly into burner head 8,emerging therefrom through burner head slots 29, at the exterior ends ofwhich it burns. The preheating means may also serve as a pilot forigniting the mixture of fuel vapors and air emerging from the burnerhead slots in starting the burner operation. The control valve 10 isused to establish the desired rate of combustion at the face of theburner head. Heat produced by the combustion of the mixture of fuelvapors and air in most cases will be conducted away sufficiently rapidlyby Whatever equipment is being heated to prevent excessive buildup ofheat and pressure in the fuel tank. The top shield assembly 13 assistsin preventing excessive buildup of pressure in the fuel tank. However,enough heat passes back to the fuel tank to maintain suflicient pressuretherein to maintain flow of liquid fuel into the generator assemblywithout requiring air pressure once the burner is in operation.

If the burner unit should be operated within the confines of a fieldrange cabinet or field oven or the like or under other conditionswhereby the temperature, and therefore the pressure, increases in thefuel tank to dangerous levels, i.e. levels substantially in excess ofnormal, as described above, the indented portion 15 of the fuel tankexpands or deforms outwardly to a position shown in broken lines as 15'in FIGURE 3. This movement of the indented portion causes the connectingmember 26 to move to a position shown in broken lines as 26' in FIGURE3, arm 27 of the connecting member taking the new position shown inbroken lines as 27'. This movement of connecting member 26 and arm 27causes the fuel feed tube 23 to bend toward indented portion 15 to aposition shown in broken lines as 23 in FIGURE 3. If the pressure issufiiciently great in the fuel tank, tube 23 ruptures at weakenedportion 24 before rupture of the fuel tank occurs. Reduction of thepressure in the fuel tank begins immediately upon rupture of the fuelfeed tube and the resulting cessation of flow of liquid fuel from thefuel tank into the generator assembly. The flame is not instantaneouslyextinguished since under the high temperature condition some vapors ofthe fuel will continue to flow from the vapor space above the liquidfuel in the fuel tank through the ruptured fuel feed tube, the generatorassembly, and the mixing chamber assembly to the burner head and willburn for a short time. However, after a short time, the flame will beextinguished due to lack of sufficient fuel passing through the burnerunit to maintain operation thereof. Thus the danger of explosion of thefuel tank is greatly reduced.

Resumption of use of the burner unit after rupture of the fuel feed tuberequires replacement of the damaged fuel tank and fuel feed tube with anew fuel tank having its indented portion and connecting member properlydisposed to cooperate with a new fuel feed tube having a weakenedportion, as described above. Replacement of the fuel tank and fuel feedtube is much less costly than the replacements which would be requiredif the fuel tank exploded, not to mention the potential savings in termsof lives or personal injuries which are accomplished by the safetydevice of the invention.

The safety device of the invention has the additional significantadvantage of being substantially tamper-proof. It cannot be readilyby-passed or rendered inorperative since the indented portion of thefuel tank and the connecting member are built into the interior of thetank, out of reach of potential tamperers. Once the fuel feed tube isconnected to the fuel tank, the connecting member and the fuel feed tubepassing therethrough are enclosed by the fuel tank, only the automaticoperation of the safety device under excessive pressure conditions, asdescribed above, will bring about any change in the arrangement of theseveral parts of the safety device.

While the present invention is particularly useful in conjunction withthe gasoline fired field range burner units herein described, it canalso be used as a safety device in other types of burners or heatersemploying liquid fuels, such as gasoline, kerosene, or other volatilefuels, whenever there is a possibility of an excessive build-up oftemperature and pressure of fuel vapors in the fuel tank of suchequipment as the result of heat being reflected, radiated, or conductedback to the fuel tank and fuel feed tubefrom the burner or generator orobjects being heated.

It will be understood that various changes in details, materials ofconstruction, steps and arrangements of parts, which have been hereindescribed and illustrated in order to explain the nature of theinvention, may be made by those skilled in the art within the principleand scope of the invention as expressed in the appended claims.

I claim:

1. A safety device for a liquid fuel burner having a reservoir capableof being filled with liquid fuel under pressure up to a predeterminedlevel providing a vapor space above said liquid fuel in said reservoircomprising a fuel feed tube for conducting liquid fuel from saidreservoir to said burner, said fuel feed tube being mechanicallyrupturable at a predetermined point within said vapor space, and meansmounted within said reservoir for movement against said tube to rupturesame upon the occurrence of a predetermined pressure within saidreservoir whereby the flow of liquid fuel from said reservoir to saidburner is cut off upon the occurrence of said predetermined pressurewithin said reservoir.

2. A safety device as in claim 1 wherein said fuel feed tube has aweakened portion in its sidewall at a point within said vapor space atwhich point said fuel feed tube ruptures on being deformed apredetermined amount.

3. A safety device as in claim 2 wherein said weakened portion in thesidewall of said fuel feed tube comprises a V-shaped circumferential cutin the exterior surface thereof.

4. A safety device as in claim,1 wherein said means mounted within saidreservoir comprise an arm having one end attached to the wall of saidreservoir and having an opening in the other end thereof for receivingthe portion of said fuel feed tube lying below said predetermined pointthereon whereby upon predetermined deformation of said reservoir wallunder the influence of internal pres sure, movement of said arm willcause said tube to rupture at said predetermined point thereon.

5. A safety device as in claim 4 wherein a portion of the wall of saidreservoir is indented, said one end of said arm being attached to saidindented portion.

References Cited FOREIGN PATENTS 555,283 1/1957 Italy.

WILLIAM F. ODEA, Primary Examiner R. GERARD, Assistant Examiner US. Cl.X.R.

